1. Field of the Invention
The present invention relates to a substrate processing apparatus and a substrate processing method, and more particularly, to a substrate processing apparatus and a substrate processing method for processing substrates in a processing chamber using a hydrogen fluoride gas.
2. Description of the Related Art
In a method for manufacturing semiconductor devices from a silicon wafer (hereinafter simply referred to as the “wafer”), there are successively and cyclically carried out a film formation step, such as chemical vapor deposition (CVD), wherein a conductive film or an insulating film is formed on a surface of the wafer; a lithography step wherein desired patterns of a photoresist layer is formed on the conductive film or the insulating film thus formed; and an etching step wherein the conductive film is shaped into gate electrodes or wiring trenches and contact holes are formed in the insulating film by plasma produced from a processing gas using the photoresist layer as a mask.
In some electronic device manufacturing method, a polysilicon layer formed on a wafer is etched. In this case, a deposit film composed primarily of SiO2 is formed on the side surfaces of trenches (grooves) formed in the wafer.
This deposit film can cause problems, such as a conduction failure, for electronic devices and hence must be removed. As a method for deposit layer removal, there is known a substrate processing method wherein a chemical oxide removal (COR) treatment and a post heat treatment (PHT) are performed on the wafer. The COR treatment causes SiO2 in the deposit layer to chemically react with gas molecules to produce a product. The PHT treatment heats up and sublimates the product on the wafer produced by the chemical reaction in the COR treatment, thereby removing the product from the wafer.
As a substrate processing apparatus for implementing this substrate processing method comprised of COR and PHT treatments, there is known a substrate processing apparatus having a chemical reaction treatment apparatus and a heat treatment apparatus connected thereto (see, for example, Japanese Patent Laid-open No. 2005-39185).
The chemical reaction treatment apparatus has a processing compartment (chamber) for housing wafers, a gas supply system for supplying a hydrogen fluoride gas into the chamber as a processing gas, and an exhaust control system for exhausting gases and the like within the chamber and controlling the internal pressure thereof.
In this chemical reaction treatment apparatus, the above-described chemical reaction treatment is performed on a wafer housed in the chamber by controlling the internal pressure of the chamber to 133 Pa (1 Torr) or higher using the exhaust control system and supplying a hydrogen fluoride gas into the chamber using the gas supply system. At this time, a pressure control valve having a relatively small bore, such as an adaptive pressure control (APC) valve, must be used in order to control the internal pressure of the chamber to 133 Pa (1 Torr) or higher.
In addition, if the hydrogen fluoride gas remains within the chamber when the chamber is communicated with another chamber, the remaining hydrogen fluoride gas may diffuse into the other chamber and cause a problem since the hydrogen fluoride gas is highly reactive. Accordingly, the hydrogen fluoride gas must be exhausted as much as possible from the chamber after the completion of the chemical reaction treatments. Furthermore, the hydrogen fluoride gas is preferably exhausted from the chamber at a high rate from the viewpoint of throughput improvement. Under normal conditions, a turbo molecular pump (TMP) must be used in order to exhaust the hydrogen fluoride gas at a high rate and as much as possible.
However, since the exhaust control system described above uses a pressure control valve having a relatively small bore, the exhaust conductance of the exhaust control system is small. In addition, the upstream pressure of the exhaust control system is as high as 133 Pa (1 Torr) or greater. In general, a TMP is adapted to fulfill its function when applied to an exhaust control system having a large exhaust conductance. Furthermore, the TMP must be used in a low-pressure environment since it may suffer damage when used in a high-pressure environment. Accordingly, it is not possible to apply the TMP to the above-described exhaust control system and, consequently, it is not possible to exhaust gases within the chamber at a high rate.
On the other hand, when a pressure control valve having a relatively large bore is used in order to apply the TMP to the exhaust control system, i.e., in order to increase the exhaust conductance of the exhaust control system, it is in principle not possible for the pressure control valve having a relatively large bore to perform high-pressure control. Consequently, it is not possible to control the internal pressure of the chamber to the aforementioned high pressure of 133 Pa (1 Torr) or greater.